WI0R wrote in message <1998031921235700.QAA02830@ladder03.news.aol.com>...

>Does the AI meter coupling lever on the F3 have to be
>locked up for the 500 f8 reflex?

No.

>Can't see that
>the lever does anything, since the 500 f8 has
>nothing that makes contact with it when mounted,
>whether it is up or down.

Correct.

>In general, does the meter coupling lever do anything
>other than allow AI/AIS lenses to mechanically tell
>the F3 what it's maximum aperture is? (Don't know
>whether I asked this right or not.)

And what the relative stop is that is being used...

>And if a lens doesn't
>make contact with the meter coupling lever whether
>up or down, what is it that is not occuring when you
>mount a Reflex lens with a fixed aperture and no
>mechanical contact with the lever? Someone please
>explain all this. I'm confused.


The F3 (and others with the same provision) assume
the lens to be an unknown "f5.6" lens, and it tells
you what shutter speed is appropriate for use with
the amount of light coming through the fixed-aperture
lens like the mirror, through a manually stopped-down
non-coupled lens, or through whatever (reversed lens,
lens on bellows, etc.). With the coupling disabled,
meter at whatever stop will be used for shooting
(using the DOF preview button, if necessary, to stop
the lens down to the taking aperture).
The coupling simply provides an electrical-mechanical
analogue for the diaphragm having been stopped down
(without it actually having been stopped down - SLR's
generally take exposures through the wide open lens,
but the meters must be compensated for the difference
between the light coming through the wide open lens,
and what the lens would pass if it were stopped down
to the taking stop during metering). BTW, disabling
the meter coupling removes errors in the marked stops
vs. the actual diaphragm openings, and between the
actual stop and the electrical analogue of that
stop. This can provide greater metering accuracy if
you take steps to keep stray light from entering the
camera eyepiece.
--
David Ruether
http://www.fcinet.com/ruether
ruether@fcinet.com